Subchannel Analysis of Fuel Assemblies of European Experimental ADS

In the frame of the European PDS-XADS (Preliminary Design Study-EXperimental Accelerator-Driven System) project, two concepts of a subcritical reactor core cooled by liquid lead-bismuth eutectic (LBE) were proposed. In this paper, the local thermal-hydraulic behavior of both LBE-cooled reactor-core concepts was analyzed. For this purpose, the MATRA subchannel analysis code (Multichannel Analyzer for Steady States and Transients in Rod Arrays) was selected, and modification was made for its applications to XADS conditions. Compared to the small-core concept, the large-core concept has a much lower hydraulic resistance, lower local coolant velocity, and lower temperatures of coolant and fuel pins. This enables the natural convection approach for removing reactor heat and for short-term realization of the core design using available technologies. The fuel assembly of the small-core concept has a tight configuration that leads to a high flow velocity and high pressure drop. The high power density of the small core results in high local temperatures of coolant, cladding, and fuel. Both coolant velocity and cladding temperature are such that special attention has to be paid to avoid corrosion and erosion damage of cladding materials. A parametric study shows that under the parameters considered, the mixing coefficient has the biggest effect on the coolant temperature distribution, whereas the cladding temperature is strongly affected by the selection of heat transfer correlations.